From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Mon, 30 Dec 2019 18:24:06 +0000 (-0700)
Subject: Simplify the code a bit.
X-Git-Tag: v9.2.0-rc1~758^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a1983b6b8ea60a41c83c5cff79ac83928b7e8c69;p=dealii.git

Simplify the code a bit.

In earlier versions of deal.II, the SparseDirectUMFPACK could deal
with block matrices but not block vectors, and so we needed to do some
copying around. This is no longer necessary.
---

diff --git a/tests/umfpack/umfpack_09.cc b/tests/umfpack/umfpack_09.cc
index a161190fe2..5ed20f4040 100644
--- a/tests/umfpack/umfpack_09.cc
+++ b/tests/umfpack/umfpack_09.cc
@@ -129,21 +129,26 @@ test()
       solution.block(2).reinit(dof_handler.n_dofs() -
                                2 * (dof_handler.n_dofs() / 3));
       solution.collect_sizes();
+
+      // Pick a solution vector
+      for (unsigned int j = 0; j < dof_handler.n_dofs(); ++j)
+        solution(j) = j + j * (i + 1) * (i + 1);
+
+      // Then choose as rhs for the linear system the vector
+      //   b = B*solution
+      // so that later the solution of the linear system Bx=b
+      // is again
+      //   x = solution
       BlockVector<double> x;
       x.reinit(solution);
       BlockVector<double> b;
       b.reinit(solution);
 
-      for (unsigned int j = 0; j < dof_handler.n_dofs(); ++j)
-        solution(j) = j + j * (i + 1) * (i + 1);
-
       B.vmult(b, solution);
       x = b;
-      Vector<double> tmp(solution.size());
-      tmp = x;
-      SparseDirectUMFPACK().solve(B, tmp);
-      x = tmp;
+      SparseDirectUMFPACK().solve(B, x);
 
+      // Check that we really got what we expected
       x -= solution;
       deallog << "relative norm distance = " << x.l2_norm() / solution.l2_norm()
               << std::endl;